Conventionally, exhaust-gas-driven turbochargers of drive apparatuses of motor vehicles may be electrically assisted so that, in particular, a delayed pressure buildup at low rotation speeds of the reciprocating-piston engine can be overcome. The exhaust-gas-driven turbocharger is driven at least at times by the electrical machine, so that the power output of the exhaust-gas-driven turbocharger is independent of the exhaust gas of the reciprocating-piston engine which is available for drive purposes. The use of so-called “media gap” machines has proven to be an advantageous solution for integrating an electrical machine into the exhaust-gas-driven turbocharger. A media gap machine is notable for a comparatively large air gap between stator and rotor which, when correctly utilized, is usable for guidance of a medium. In the context of utilization in an exhaust-gas-driven turbocharger, the media gap machine is integrated in such a way that it is located in an intake duct of the exhaust-gas-driven turbocharger, so that the air to be delivered flows through the aforementioned air gap. This enables particularly compact integration of the electric motor into the turbocharger.
As the electrification of motor vehicles progresses, the recovery of electrical energy also becomes increasingly important. Conventionally, the media gap machine may be operated in generator mode in order to recover energy, the drive force then being made available in generator mode, in particular, by the exhaust gas of the reciprocating-piston engine. This application has hitherto been sensible, however, only during normal operation or on-load operation of the reciprocating-piston engine, since only then is sufficient drive energy made available for the exhaust-gas-driven turbocharger by the exhaust gas of the reciprocating-piston engine.